﻿using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;

namespace XDL.Framework.Graphics
{
    public abstract class ImprovedPerlinTexture<SurfaceFormatType> :
            Texture2D where SurfaceFormatType : struct
    {
        static int[] p = new int[512];
        static int[] permutation = { 151,160,137,91,90,15,
       131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,
       190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,
       88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166,
       77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,
       102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196,
       135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123,
       5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,
       223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9,
       129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228,
       251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107,
       49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,
       138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180
       };

        static ImprovedPerlinTexture()
        {
            for (int i = 0; i < 256; i++) p[256 + i] = p[i] = permutation[i];
        }

        /// <summary>
        /// Creates new Perlin-based texture
        /// </summary>
        /// <param name="graphicsDevice">Graphic device</param>
        /// <param name="w">Width of the texture.</param>
        /// <param name="h">Height of the texture.</param>
        /// <param name="format">Texture format, see <see cref="SurfaceFormat"/>.</param>
        public ImprovedPerlinTexture(GraphicsDevice graphicsDevice, int w, int h, SurfaceFormat format)
            :
            base(graphicsDevice, w, h, true, format)
        {
        }

        public Vector3 Scale = Vector3.One;

        double Noise(double x, double y, double z)
        {
            int X = (int)Math.Floor(x) & 255,                  // FIND UNIT CUBE THAT
                Y = (int)Math.Floor(y) & 255,                  // CONTAINS POINT.
                Z = (int)Math.Floor(z) & 255;
            x -= Math.Floor(x);                                // FIND RELATIVE X,Y,Z
            y -= Math.Floor(y);                                // OF POINT IN CUBE.
            z -= Math.Floor(z);
            double u = Fade(x),                                // COMPUTE FADE CURVES
                   v = Fade(y),                                // FOR EACH OF X,Y,Z.
                   w = Fade(z);
            int A = p[X] + Y, AA = p[A] + Z, AB = p[A + 1] + Z,      // HASH COORDINATES OF
                B = p[X + 1] + Y, BA = p[B] + Z, BB = p[B + 1] + Z;      // THE 8 CUBE CORNERS,

            return Lerp(w, Lerp(v, Lerp(u, Grad(p[AA], x, y, z),  // AND ADD
                                           Grad(p[BA], x - 1, y, z)), // BLENDED
                                   Lerp(u, Grad(p[AB], x, y - 1, z),  // RESULTS
                                           Grad(p[BB], x - 1, y - 1, z))),// FROM  8
                           Lerp(v, Lerp(u, Grad(p[AA + 1], x, y, z - 1),  // CORNERS
                                           Grad(p[BA + 1], x - 1, y, z - 1)), // OF CUBE
                                   Lerp(u, Grad(p[AB + 1], x, y - 1, z - 1),
                                           Grad(p[BB + 1], x - 1, y - 1, z - 1))));
        }
        double Fade(double t) { return t * t * t * (t * (t * 6 - 15) + 10); }
        double Lerp(double t, double a, double b) { return a + t * (b - a); }
        double Grad(int hash, double x, double y, double z)
        {
            int h = hash & 15;                      // CONVERT LO 4 BITS OF HASH CODE
            double u = h < 8 ? x : y,                 // INTO 12 GradIENT DIRECTIONS.
                   v = h < 4 ? y : h == 12 || h == 14 ? x : z;
            return ((h & 1) == 0 ? u : -u) + ((h & 2) == 0 ? v : -v);
        }

        /// <summary>
        /// Generates the texture.
        /// </summary>
        public void Fill()
        {
            SurfaceFormatType[] texels = new SurfaceFormatType[this.Width * this.Height];
            BeginPass(texels);
            for (int pass = 0; pass < PassCount; pass++)
            {
                for (int i = 0; i < texels.Length; i++)
                {
                    int x = i % this.Height;
                    int y = i / this.Width;
                    double azimuthAngle = 2 * Math.PI * (x / (double)this.Width);
                    double polarAngle = Math.PI * (y / (double)this.Height);
                    SurfaceFormatType texel = ConvertNoiseToTexel(
                        Noise(
                            Scale.X * Math.Sin(polarAngle) * Math.Cos(azimuthAngle),
                            Scale.Y * Math.Sin(polarAngle) * Math.Sin(azimuthAngle),
                            Scale.Z * Math.Cos(polarAngle)), x, y);                    
                    // 
                    texels[i] = TexelOp(texels[i],texel);
                }
            }
            EndPass(texels);
            // copy the colors
            this.SetData<SurfaceFormatType>(texels);
        }

        protected virtual void BeginPass(SurfaceFormatType[] texels)
        {
        }
        protected virtual void EndPass(SurfaceFormatType[] texels)
        {
        }
        protected virtual SurfaceFormatType TexelOp(SurfaceFormatType currentTexel, SurfaceFormatType texel)
        {
            return texel;
        }
        protected virtual int PassCount
        {
            get { return 1; }
        }

        /// <summary>
        /// Convert the noise value into a <typeparamref name="SurfaceFormatType"/> value.
        /// </summary>
        /// <param name="noiseValue">The perlin noise value.</param>
        /// <param name="x">X (in texture pixel space)</param>
        /// <param name="y">Y (in texture pixel space)</param>
        /// <returns>A color.</returns>
        protected abstract SurfaceFormatType ConvertNoiseToTexel(double noiseValue, int x, int y);
    }
}
